1. Technical Field of the Invention
The present invention relates to an apparatus and a method for removing unburned carbon from fly ash, and more particularly to an apparatus and a method for efficiently removing unburned carbon from fly ash generated in coal firing power plants and so on, and effectively using the removed unburned carbon and the fly ash from which unburned carbon is removed.
2. Description of the Related Art
Fly ash generated in coal firing power plants etc. is used for materials for cement and artificial lightweight aggregates, concrete admixture, etc. However, when fly ash is used as concrete admixture, unburned carbon of fly ash will absorb AE water reducing agent etc., and will reduce the workability of the concrete. And, at the time of placing of the concrete, unburned carbon comes floating and there is harmful influence of a black part occurring in the connecting portion of the concrete. Further, when there was much unburned carbon of fly ash, there was also a problem that the quality of an artificial lightweight aggregate deteriorated. Therefore, only fly ash with little unburned carbon was used for the materials of cement etc., and the fly ash with high unburned carbon content could not be used effectively and was processed for reclamation as industrial waste.
In order to remove unburned carbon from fly ash of high-unburned carbon content and to effectively use them, in the first patent document, a method for removing unburned carbon from fly ash is described. This method comprises the steps of: adding water to fly ash to produce slurry; adding collector to the slurry; feeding the slurry and the collector to a submerged agitator having a rotation shaft penetrating a cylindrical main body in an axial direction thereof, plurality of chambers formed by dividing an inside of the main body in the axial direction thereof and an agitating vane fixed to the rotation shaft and rotating in each chamber to add shearing force to the slurry and collector; adding frother to the slurry and collector; agitating them to generate air bubbles; and adhering unburned carbon of the fly ash to the air bubbles to raise the unburned carbon.
With this method, by adding shearing force to original fly ash slurry, which contains unburned carbon and to which collector is added before flotation process, unburned carbon content of the fly ash can considerably reduced, and fly ash with approximately 0.5% of unburned carbon content can be obtained. In addition, generally used collector such as kerosene can be used in the above process, and the amount of collector used can be reduced, which allows little kerosene etc. to remain in the fly ash as a product and post-processing after the flotation process to be easy.
Patent document 1: Japanese Patent No. 3613347 gazette.